Quite right there. Grunge is not even a genre, not in the true sense of the word, since musical genres by their nature spread worldwide, and tend to run and run and run, often for decades, or even in some cases centuries!!... but even if it ever was, then it is now dead. It's just an umbrella term which some guy dreamed up once and was used to describe bands from one particular tiny localised scene from a small area of the Pacific NW, and who all became popular in that particular period of time. The very term "grunge" is a nebulous one at best, because there is no actual 'grunge' sound - Pearl Jam sounds nothing like Soundgarden, who sounds nothing like Nirvana, who sounds nothing like Alice in Chains. And people who label an innovative and diverse and uncompromising band like PJ - who continually re-invent themselves musically - as simply 'grunge' do so simply because they can't appreciate the complex, reflective, experimental, and actually quite 'progressive' nature of much of their music, especially from the 3rd 'Vitalogy' album onwards, and they obviously can't hear beyond the first couple of albums, which were both very heavily over-produced pseudo-metal affairs, and which the band subsequently actually hated, and are a million miles away from the music they've been making since about 1994. Pearl Jam has never been a band to be boxed into formulaic songwriting, or pinned down with any simple-minded categorizations, or at least not by anyone who wants to be taken seriously. And you will never find any quote in any interview with Eddie Vedder where he ever says "yes, we are/were a grunge band".
Not sure how Kiss got in on this topic. I don't understand the whole Kiss Industry, or why it even has to exist, but I wouldn't call a band with their success as 'over-rated', Kiss I admit are a lot of fun and - unlike Nirvana, who came and went inside 3 or 4 years, Kiss with their 40+ years of touring and recording have earned the right to be respected if only for their hard work and longevity.